The opinion was requested by the Washington Liquor Control Board, which has been concerned that such local bans could restrict access to legal marijuana and make it difficult to move people away from the black market.

Some jurisdictions, including unincorporated Pierce County, Lakewood and Wenatchee, have effective bans on pot businesses, because their local ordinances require businesses to follow state, federal and local law, and marijuana remains illegal under federal law.

Nearly three dozen of the state's 75 biggest cities, from Redmond to Pullman, have adopted moratoriums of up to a year on marijuana businesses.